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Vitamin D Fact Sheet

What You Need To Know About Vitamin D

According to the Institutes of Medicine, there are few naturally occurring food sources of vitamin D. For those who do not get regular sun exposure, a supplement or supplemented food is likely needed.

Ten minutes of sunshine on your arms provide 10,000 IUs of vitamin D, compared with 100 IUs of vitamin D from a fortified beverage. While the upper limit of vitamin D consumption considered safe is set at 4,000 IUs, there is no toxic level of vitamin D that can be received from sunlight.

U.S. federal law requires infant formula to be supplemented with vitamin D and to contain 40 to 100 IUs per 100 calories, compared with breast milk which contains approximately 4 IUs of vitamin D per 100 calories. For this reason, the American Academy of Pediatrics recommends 400 IUs of vitamin D supplementation per day for breastfeeding babies, beginning a few days after birth.

Vitamin D is more accurately recognized as a “prohormone,” as opposed to a vitamin, because it can be synthesized by the body with the activation of sunlight.

Factors that decrease vitamin D activation in the skin include sunscreen, colder seasons, latitudes further from the equator, and darker skin color.